1. Field of she Invention
The present invention relates to a method of forming; an oxide-ceramics film to be applied to an electronics device using the ferroelectricity, piezoelectricity, pyroelectricity, conductivity, transducency, and capacity of the film.
2. Description of the Related Art
As related art pertaining to the present invention, there is a paper reported in the Japanese Journal of Applied Physics 1997, Volume 36, pages 5803-5807. With respect to the method of forming a lead zirconate titanate (xe2x80x9cPZTxe2x80x9d) ceramics film of such related art, the PZT film is formed by dip-coating an organometallic compound solution (sol) on a substrate, drying it at 110xc2x0 C., pyrolyzing it at 350xc2x0 C., and crystallizing it at 500xc2x0 C. These heat-treatment processes are usually carried out in air or oxygen.
Nevertheless, according to the method of forming PZT films in the aforementioned related art, it is difficult to control the amount of oxygen in the film during the heat-treatment processes of drying, pyrolyzing, and crystallizing carried out under air- or oxygen-atmosphere. In an experiment conducted by the present inventors, for example, the sol used was prepared by dissolving lead acetate (II) tri-hydrate, zirconium acetyl acetonate, and titanium tetra-isopropoxide with 2-n-butoxyl ethanol, and further adding polyethylene glycol. The sol was then spin-coated onto a substrate, dried, pyrolyzed, and crystallized all in air. The PZT film suffered approximately 40% of oxygen deficiency in comparison with the sol stoichiometric composition.
The present invention was devised in view of the foregoing problems of the conventional art, and an object thereof is to provide a method of forming an oxide-ceramics film capable of controlling the amount of oxygen in the film and with little oxygen deficiency.
Another object of the present invention is to provide a method of forming an oxide-ceramics film which prevents the escape of oxygen during the preparation process.
In order to achieve the aforementioned objects, the method of forming the oxide-ceramics film according to the present invention is characterized by the following points.
(1) In a method of forming an oxide-ceramics film comprising a step of forming an amorphous film on an arbitrary substrate and a step of heating the arbitrary substrate and amorphous film for crystallization, at least one or more of the steps among the step of forming an amorphous film, the step of heating the amorphous film for crystallization, and the step of these processings to be conducted thereafter include a step of processing under an atmosphere including moisture.
In the present invention, xe2x80x9catmosphere including moisturexe2x80x9d shall include a 100% water atmosphere such as inside a water tank as well as an aqueous vapor atmosphere.
(2) The step of processing under an atmosphere including moisture uses supercritical water as the moisture.
(3) The step of forming an amorphous film uses a sol-gel method or sputtering method. The sol-gel method includes a step of coating a sol solution on the arbitrary substrate and a step of drying the coated sol solution.
(4) The oxide-ceramics film is a lead zirconate titanate film.
(5) When performing the step of processing under an atmosphere including moisture during the heat-treatment process, the moisture is 100% water.
(6) The step of processing under an atmosphere including moisture is performed upon setting the pressure of the atmosphere lower than 200 atmospheric pressure.
(7) The temperature of the heat-treatment process is set at 700xc2x0 C. or lower.
(8) In a method of forming an oxide-ceramics film comprising a step of forming an amorphous film on an arbitrary substrate and the step of crystallizing the amorphous film, the amorphous film is crystallized by hydrothermal treatment being performed under water.
(9) During the step of crystallizing the amorphous film, hydrothermal treatment is performed upon using water in which pH is adjusted to 7.
(10) During the step of crystallizing the amorphous film, hydrothermal treatment is performed upon setting the pressure in a range between 2 and 20 atmospheric pressure.
(11) During the step of crystallizing the amorphous film, hydrothermal treatment is preformed upon setting the temperature in a range between 120xc2x0 C and 250xc2x0 C.
Examples of the present invention are explained in detail below.